In children, the most common cause of OSA/H is believed to be tonsillar hypertrophy. We hypothesize that in children, similar to adults, OSA/H is secondary to narrowing of the pharyngeal area. Tonsillar hypertrophy is only one factor that exacerbates this underlying abnormality. We also hypothesize that OSA/H impairs children's growth and congnitive function. We propose to examine and correlate respiratory function and upper airway anatomy in children with OSA/H using PSG and MRI studies. Growth and cognition will also be assessed.